Although attention-deficit/hyperactivity disorder (ADHD) is an impairing condition in girls, research focused on the long-term, prospective follow-up of girls with ADHD is extremely rare. The chief objective of this proposal is to perform a rigorous, prospective, 10-year follow-up investigation of a well-characterized, ethnically and socioeconomically diverse sample of girls with ADHD (n = 140), plus an age- and ethnicity/ race-matched sample of comparison girls (n = 88), who were initially ascertained and studied in naturalistic research summer programs between the ages of 6 and 12 years (Wave 1) and who received an extensive 5-year follow-up in early to mid-adolescence (Wave 2), which featured a retention rate of 92% of the sample. Key aims for the Wave 3 assessments, during late adolescence/young adulthood, are to (a) characterize outcomes of these individuals across multiple domains of functioning: ADHD symptoms, externalizing and internalizing symptoms (including antisocial behavior, mood disturbance, and eating pathology), substance use/abuse, academic performance, neuropsychological skills, peer and family relations, accidental injury, and service utilization; (b) describe and understand trajectories of development from childhood through early adulthood; (c) relate academic and social functioning to the continued presence of executive functioning deficits; and (d) explain patterns of pathology and resilience during this crucial developmental period that encompasses the expected transition to independent functioning. It is predicted that girls with ADHD will be at risk for a wider range of pathology and impairments than boys with ADHD, necessitating the assessment of a diverse array of outcome variables. The proposed investigation features psychometrically rigorous, multi-method, and multi-informant evaluations, utilizing staff who will be unaware of the initial diagnostic status of the participants. Given the increasing evidence for the difficult long-term outcomes of males with ADHD, understanding female outcomes and developmental trajectories is a clinical and scientific priority.